The American National Standard for Methods of Measurement of Compatibility between Wireless Communication Devices and Hearing Aids (ANSI C63.19-2001) standard describes the requirements of wireless communications with respect to interference and hearing aids. The standard requires that mobile handsets not interfere with hearing aids in order to be deemed hearing aid compatible (“HAC”). The Federal Communications Commission on Jan. 10, 2003 required that manufacturers and service providers make digital wireless phones accessible to hearing-impaired individuals who require hearing aids.
Mobile handsets (e.g., digital wireless phones), in addition to radiating radio frequency energy (RF) from antennas configured therewith, often radiate other forms of energy. For example, a mobile handset is generally configured with a battery that provides electrical energy to circuitry of the handset. This electrical energy results in electric fields (E-fields) and magnetic fields of varying intensities about the mobile handset. More substantially, however, RF currents emanating from the RF module of the handset propagate through conductive parts of the mobile handset (e.g., metal components such as wires) and result in E-fields and magnetic fields that interfere with hearing aids. In a clamshell type mobile handset (i.e., a mobile handset that folds, also known as a flip-phone), E-fields and magnetic fields may be particularly strong near each of the microphone portion and the speaker portion of the handset. These E-fields and magnetic fields often interfere with hearing aids and prevent a hearing-impaired user from improperly communicating via the handset.